19909928921 has 4 divisors (see below), whose sum is σ = 19911813072. Its totient is φ = 19908044772.

The previous prime is 19909928911. The next prime is 19909928953. The reversal of 19909928921 is 12982990991.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12982990991 = 31 ⋅418806161.

It is a cyclic number.

It is not a de Polignac number, because 19909928921 - 2³⁴ = 2730059737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19909928911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 926135 + ... + 947388.

It is an arithmetic number, because the mean of its divisors is an integer number (4977953268).

Almost surely, 2^19909928921 is an apocalyptic number.

It is an amenable number.

19909928921 is a deficient number, since it is larger than the sum of its proper divisors (1884151).

19909928921 is a wasteful number, since it uses less digits than its factorization.

19909928921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1884150.

The product of its (nonzero) digits is 1889568, while the sum is 59.

The spelling of 19909928921 in words is "nineteen billion, nine hundred nine million, nine hundred twenty-eight thousand, nine hundred twenty-one".